This invention relates to a contact copying apparatus, and especially such an apparatus utilized to duplicate microfiche.
A microfiche, which is a sheet of film containing miniature images such as many pages of a document, can be duplicated by the contact printing method. My earlier patent application Ser. No. 652,635, filed Jan. 26, 1976, describes a microfiche duplicator which can utilize a bank of fluorescent aperture lamps at the exposure station where light shines through the master microfiche onto the copy sheet microfiche. However, where more rapid duplication is required, a jacketed mercury vapor lamp may be utilized, which can produce more light but which must be left on for extended periods and utilized with a shutter. Such a lamp is typically of elongated shape, with a short arc tube which can lie directly under the position where the microfiche are held, and is utilized with a substantially parabolic reflector extending around the axis of the lamp to reflect collimated light towards the microfiche. This arrangement produces uneven illumination of the microfiche, with the end portions of the microfiche which lie over or beyond opposite ends of the lamp, receiving a lower level of illumination than the middle portion of the microfiche. Additional reflectors can be utilized to increase the illumination at the end portions of the microfiche, but such reflectors would have to lie close to the lamp to capture significant amounts of light and provide collimated light at the microfiche, and would have to avoid interference with the shutter mechanism.